The present invention relates to a lens moving mechanism for retaining and moving a lens barrel of a liquid crystal projector, and to a liquid crystal projector employing the same.
FIG. 1 is an illustration showing a structural example of a conventional liquid crystal projector. In the drawing, a numeral 1 designates a light source consisting of a lamp such as a metal halide lamp, numerals 2 and 3 designate dichroic mirrors for splitting light, numerals 4 and 5 designate reflection mirrors, numerals 6, 7, and 8 designate liquid crystal panels, numerals 9 and 10 designate dichroic mirrors for recombining lights, a numeral 11 designates a light path adjusting mechanism consisting of a pair of liquid crystal prisms 12A and 12B, and a numeral 13 designates a projection lens. All of these are arranged inside a projector casing 14.
The light emitted from the light source 1 is split by dichroic mirrors 2 and 3 into lights of three primary colors, that is, red (R), blue (B), and green (G). Each of the split lights is modulated for its transmittance by the corresponding liquid crystal panel 6, 7 or 8 according to image information of each color component. The liquid crystal panels 6, 7 and 8 are located in the corresponding light paths, respectively. The modulated lights are recombined by the dichroic mirrors 9 and 10.
The recombined light is adjusted for its light path by the light path adjusting mechanism 11 and is then enlarged and projected onto a screen (not shown) through the projection lens 13.
In the aforementioned conventional liquid crystal projector, the light path adjusting mechanism 11 is arranged just before the projection lens 13. This arrangement has a problem that the miniaturization is difficult, because the light path adjusting mechanism 11 requires to lengthen the distance from the respective liquid crystal panels 6, 7 and 8 to the projection lens 13 (for instance, the distance m for the liquid crystal panel 6 in FIG. 1) in the liquid crystal projector.
There is another problem. That is, lights having image information pass multiple glass plates constituting the liquid crystal prisms 12A and 12B of the light path adjusting mechanism 11 after transmitted through the liquid crystal panels 6, 7 and 8 and are then projected through the projection lens 13 so that the image is enlarged and displayed on the screen. Due to the multiple glass plates, the image distortion and chromatic aberration distortion in the image projected on the screen are increased, thus making high resolution image display impossible.
In order to solve the problem of difficulty in miniaturization and the problem that it is impossible to display a high resolution image due to increase of image distortion and chromatic aberration distortion in the projected image, for example, Japanese Unexamined Patent Publication No. H6-331953 discloses a liquid crystal projector constructed in such a manner that a lens barrel moving mechanism is provided which can move the lens barrel having the projection lens therein relative to the projector casing in a direction perpendicular to the projector casing, thus eliminating the light path adjusting mechanism which is the factor causing the difficulties in miniaturization, and in high resolution image display due to enhancement of image distortion and chromatic aberration distortion.
By structuring a liquid crystal projector in this manner, the miniaturization can be achieved, and it becomes possible as well to perform the shift- or tilt adjustment of the projected image without generation of image distortion and chromatic aberration distortion in the projected image.
It is an object of the present invention to further improve the above-described lens barrel moving mechanism of a liquid crystal projector in which the light path adjusting mechanism is eliminated, and to provide a lens moving mechanism which has a simple structure and is capable of achieving a smooth and precise movement of the lens barrel, and a liquid crystal projector employing the lens moving mechanism.
In order to achieve the foregoing object, a first invention of the present application provides a lens moving mechanism comprising: a lens retaining member for retaining a lens barrel which is provided therein with a projection lens for projecting light with the image information; a lens retaining member guiding means for guiding said lens retaining member movably in at least one direction of axis which is perpendicular to the optical axis of said light; a fixed supporting member for supporting said lens retaining member guiding means; and a driving means for applying a driving force to the lens barrel, wherein said lens retaining member guiding means comprises: a track member which is provided with a rolling member running surface extending along the longitudinal direction thereof; a movable member which is incorporated in said track member such that the movable member is movable relative to said track member and is provided with a rolling member running surface corresponding to the rolling member running surface of said track member; and a plurality of rolling members arranged between the rolling member running surface of said track member and the rolling member running surface of said movable member.
Since the lens retaining member guiding means has the aforementioned structure, that is, comprising a track member which is provided with a rolling member running surface extending along the longitudinal direction thereof, a movable member which is incorporated in the track member such that the movable member is movable relative to the track member and is provided with a rolling member running surface corresponding to the rolling member running surface of the track member, and a plurality of rolling members arranged between the rolling member running surface of the track member and the rolling member running surface of the movable member, the relative movement of the movable member to the track member is smooth because of the rolling members, thus achieving the smooth movement of the projection lens.
A second invention of the present application provides the aforementioned lens moving mechanism being characterized by further comprising an intermediate member for interconnecting said lens retaining member and said fixed supporting member, wherein said lens retaining member guiding means comprises a first guiding means arranged between said fixed supporting member and said intermediate member and a second guiding means arranged between said intermediate member and the lens retaining member, said first guiding means guides said intermediate member in a first predetermined direction, and said second guiding means guides said lens retaining member in a second predetermined direction perpendicular to said first predetermined direction, and the respective track members and the respective movable members of said first guiding means and said second guiding means are arranged at substantially the same position relative to the direction of the optical axis.
Since the respective track members and the respective movable members of the first guiding means and the second guiding means are arranged at substantially the same position relative to the direction of the optical axis as described above, the lens moving mechanism can be structured to have reduced thickness in the direction of the optical axis, thus enabling a miniaturization.
A third invention of the present application provides the aforementioned lens moving mechanism being characterized in that the track members and the movable members of the lens retaining member guiding means are arranged in such a manner that their transverse directions are substantially parallel to the direction of the optical axis.
Since the track members and the movable members of the lens retaining member guiding means are arranged in such a manner that their transverse directions are substantially parallel to the direction of the optical axis, the rigidity against the moment in the direction perpendicular to the optical axis is increased so that the heavy lens barrel can be supported with high rigidity, thereby enabling the precise and smooth movement of the lens barrel.
A fourth invention of the present application provides the aforementioned lens moving mechanism being characterized in that an interference is set between the rolling members and the rolling member running surfaces of the track member and the movable member in said lens retaining member guiding means.
By setting an interference (a minus clearance) between the rolling members and the rolling member running surfaces of the track member and the movable member in the lens retaining member guiding means as described above, the rigidity of the lens retaining member guiding means is increased, enabling a more precise and smoother movement of the heavy lens barrel.
A fifth invention of the present application provides the aforementioned lens moving mechanism being characterized in that said track member is an outer rail which is made of a plate member and substantially formed in a U-shape in a section perpendicular to the longitudinal direction thereof and to have the rolling member running surfaces on both inner sides in the transverse direction thereof, and said movable member is an inner rail which is made of a plate member and substantially formed in a U-shape in a section perpendicular to the longitudinal direction thereof and to have the rolling member running surfaces on both outer sides in the transverse direction thereof, and said lens moving mechanism further comprising a rolling member retainer which retains rotatably said rolling members.
Since the track member and the movable member are an outer rail and an inner rail made of plate members, the track member and the movable member can be formed easily by, for instance, pressing of steel sheets and inexpensive commercially available balls can be used for the rolling members. As a result, the mechanism can be fabricated at relatively low cost, achieving the cost reduction.
A sixth invention of the present application provides aforesaid lens moving mechanism being characterized in that said track member is a track rail provided with the rolling member running surfaces on both sides in the transverse direction thereof, and said movable member is a movable block provided with endless circulation passages including the rolling member running surfaces corresponding to the rolling member running surfaces of said track rail, and said rolling members are accommodated to be aligned in said endless circulation passages to circulate according to the relative movement of said movable block to said track rail.
In the structure that the track member is a track rail provided with the rolling member running surfaces on both sides in the transverse direction thereof, and the movable member is a movable block provided with endless circulation passages including the rolling member running surfaces corresponding to the rolling member running surfaces of the track rail, and the rolling members are accommodated to be aligned in the endless circulation passages to circulate according to the relative movement of the movable block to the track rail, an extremely smooth operation, that is, an extremely smooth relative movement of the movable block to the track rail can be achieved. Therefore, it is possible to smoothly move the lens barrel. In addition, since the lens retaining member guiding means composed of the track rail and the movable block has a high rigidity, the lens barrel can be supported rigidly and the lens barrel can be moved with higher precision.
A seventh invention of the present application provides a liquid crystal projector characterized by comprising a lens moving mechanism as claimed in any one of claims 1 through 6, and a projector casing which is provided therein with liquid crystal panels, wherein lights with image information from said liquid crystal panels are introduced to the projection lens retained by said lens moving mechanism.
The liquid crystal projector comprises the aforementioned lens moving mechanism, thereby achieving a compact liquid crystal projector without generation of the image distortion and the chromatic aberration distortion in the projected image.